Smoothed particle hydrodynamics in hydropower applications : modeling of hydraulic jumps

Abstract: In present thesis, the Lagrangian particle based method Smoothed ParticleHydrodynamics (SPH) is used to model two-dimensional problems associated with hydropower applications such as dam break evolution and hydraulic jumps. In the SPHmethod, the fluid domain is represented by a set of non-connected particles which possess individual material properties such as mass, density, velocity, position and pressure. Besides representing the problem domain and acting as information carriers the particles also act as the computational frame for the field function approximations. As the particles move with the fluid the material properties changes over time due to interaction with neighbouring particles. The adaptive nature of the SPH-method together with the nonconnectivity between the particles results in a method that is able to handle very large deformations as is the case for highly disordered free-surface flows such as hydraulic jumps.The dam break case was used as a model validation test case where the response of different parameter settings was explored. The SPH spatial resolution and the choice of artificial viscosity (a term in the momentum equation) constants had a major impact on the results. Increasing the spatial resolution increased the number of flow features resolved and setting the constants equal to unity resulted in a highly viscous and unphysical solution.Following the parameter study, the work focused on SPH simulations of hydraulic jumps. A hydraulic jump is a rapid transition from supercritical flow to subcritical flow characterized by the development of large scale turbulence, surface waves, spray, energy dissipation and considerable air entrainment. Several features of the jump were explored using the SPH method and good agreement with theory and experiments was obtained for e.g. the conjugate depth and the mean free surface elevation in the roller section. However, the free surface fluctuation frequencies were over predicted and the model could not capture the decay of fluctuations in the horizontal direction.